diff --git a/scheme/fd.rs b/scheme/fd.rs
new file mode 100644
index 0000000000000000000000000000000000000000..c689d550e620cc7261cc6f3477d2f82aa398c62d
--- /dev/null
+++ b/scheme/fd.rs
@@ -0,0 +1,2 @@
+/// A file descriptor type
+pub type Fd = usize;